Antiretroviral therapy (ART) has had a dramatic impact in the reduction of maternal to fetal HIV transmission in the last decade. Use of ART to treat maternal HIV infection during pregnancy or reducing mother-to-child transmission has become standard of care. However, prevention of HIV transmission requires exposing the pregnant mother and her offspring to potent ART medications and increasingly complex treatment regimes. Yet, the fetal safety of currently approved ART medications is largely unknown. Thus, there is need to evaluate the fetal toxicity of specific ART strategies. Given the overwhelming benefits of ART in HIV transmission prevention, the clinically relevant question revolve around timing (e.g., when to initiate therapy) and specific ART regime selection (e.g., which combination of drugs). The major aim of this proposal is to contribute fetal safety information to the development of evidence-based recommendations for the management of HIV-infected pregnant women that will assist clinicians and patients in their decision making process. We propose to evaluate the risk of congenital malformations and other adverse pregnancy outcomes following antenatal exposure to ART in a prospective cohort of pregnant women.